Gain Margin Specifications Research Articles

Automated approach to design predictive PI control scheme for gain margin specification

Automated approach to design predictive PI control scheme for gain margin specification

A Software Realization of Disturbance Rejection Optimal FOPID Controller Design Methodology by Using Soft Computing Techniques

This study presents a soft computing tool for the computer-aided design of disturbance rejection FOPID controllers based on the maximization of Reference to Disturbance Ratio (RDR) index. The study illustrates the utilization of software routines to implement a soft computing scheme in order to solve a closed loop disturbance rejection FOPID control system design problem for a target gain margin specification. Authors demonstrate that the complex design efforts, which involve a high level of mathematical knowledge, can be easily performed by using basic software routines when soft computing techniques are employed effectively in the computation processes. Illustrative design examples are shown to show effectiveness of the proposed design method.

A robust fractional-order controller design with gain and phase margin specifications based on delayed Bode’s ideal transfer function

In this study, a robust fractional-order controller design methodology for a type of fractional-order or integer-order model with dead time is proposed using phase and gain margin specifications. The delayed Bode’s ideal transfer function is used as a reference model to design the controller analytically. The delay term in delayed Bode’s ideal transfer function provides the exact determination of these frequency domain specifications when the system owns a dead time. The analytical robust controller design problem is transformed to solving four nonlinear equations with four unknown variables, two of which are the desired specifications; namely, phase and gain margins. The remaining two are the phase and gain cross-over frequencies. Next, some conditions are set based on the desired specifications so that nonlinear equations provide a unique solution. The proposed method is compared with the other existing robust controller methods based on the same frequency domain specifications. The simulation results reveal that the proposed method outperforms the other methods and also gives closer outcomes to the desired specifications.

Flight Control Design for a Tailless Aircraft Using Eigenstructure Assignment

We apply eigenstructure assignment to the design of a flight control system for a wind tunnel model of a tailless aircraft. The aircraft, known as the innovative control effectors (ICEs) aircraft, has unconventional control surfaces plus pitch and yaw thrust vectoring. We linearize the aircraft in straight and level flight at an altitude of 15,000 feet and Mach number 0.4. Then, we separately design flight control systems for the longitudinal and lateral dynamics. We use a control allocation scheme with weights so that the lateral pseudoinputs are yaw and roll moment, and the longitudinal pseudoinput is pitching moment. In contrast to previous eigenstructure assignment designs for the ICE aircraft, we consider the phugoid mode, thrust vectoring, and stability margins. We show how to simultaneously stabilize the phugoid mode, satisfy MIL-F-8785C mode specifications, and satisfy MIL-F-9490D phase and gain margin specifications. We also use a cstar command system that is preferable to earlier pitch-rate command systems. Finally, we present simulation results of the combined longitudinal/lateral flight control system using a full 6DOF nonlinear simulation with approximately 20,000 values for the aerodynamic coefficients. Our simulation includes limiters on actuator deflections, deflection rates, and control system integrators.

Robust stabilizing first-order controllers for a class of time delay systems

In this paper, stabilizing regions of a first-order controller for an all poles system with time delay are computed via parametric methods. First, the admissible ranges of one of the controller’s parameters are obtained. Then, for a fixed value of this parameter, stabilizing regions in the remaining two parameters are determined using the D-decomposition method. Phase and gain margin specifications are then included in the design. Finally, robust stabilizing first-order controllers are determined for uncertain plants with an interval type uncertainty in the coefficients. Examples are given to illustrate the effectiveness of the proposed method.

Self-tuning TCP traffic controller using gain margin specification

The paper proposes a self-tuning active queue management (AQM) controller for Internet protocol (IP) routers supporting transmission control protocol (TCP) traffic in the Internet. Classical control theory is applied in the design to meet the frequency-domain-specification gain margin. The user can assign a proper gain margin to achieve good AQM performance. Simple equations for obtaining the AQM controller are derived. The designed AQM controller self-tunes, only when changes in Internet traffic have drifted the traffic monitoring parameter outside its specified interval, otherwise the self-tuning AQM controller remains unchanged. The OPNET® simulations used by the authors in single and in multiple bottleneck links demonstrate that, with the use of a self-tuning AQM controller in the routers, this AQM control system adapts very well to great fluctuations in the TCP traffic, thus providing the network with good stability robustness.